1. Field of the Invention
The present invention relates to a PTC heating element with at least one PTC resistance element that is arranged between two electrically conductive plates in a housing opening of a housing and that, with at least one of the electrically conductive plates as an intermediate layer, is pressed with an initial tension against a heat-emitting element that is held by the housing.
2. Description of the Related Art
Such a PTC heating element is known, for example, from EP 0 350 528, which is traced back to the applicant. In this state of the art, a number of PTC heating elements are arranged in a frame in a number of planes with heat-emitting elements, in the form of metal strips curved in a meandering manner, layered between. Located within the frame is a spring, which presses the two electrically conductive plates lying on the exterior of the PTC heating element against the PTC element for good thermal and electrical contacting and the heat-emitting elements against the adjacent electrically conductive plate for good heat transfer of the heat generated by the PTC resistance element. In the mentioned state of the art, the PTC heating element is used for heating air. There are, however, other embodiments also known in which the PTC resistance element heats a heating plate. Such embodiments are particularly known for heating or keeping warm foods, for example, baby food.
The problem forming the basis of the present invention is to specify a heating element of this category that can be manufactured simply and therefore economically.
To solve this problem, the present invention specifies a PTC heating element with the characteristics of Claim 1. This differs from the category-defining state of the art by a housing opening, whereby attachment tabs that are arranged around the edge of the housing opening protrude from it and whereby the heat-emitting element has tab cuts behind which the tabs engage when a heat-emitting element is mounted on the housing.
As a result of this engaging, the heat-emitting element is connected to the housing in a simple manner, for example, by being locked in place. Alternatively, the tabs can also have a thickening on their free end that engages behind the tab opening, whereby this thickening is formed by surface-fusing the respective tab. Such thickened tabs are achieved, for example, by hot stamping.
The tabs, however, serve more than just to attach the heat-generating element to the housing. Rather, the tabs encircle the housing opening and protrude from the exterior of the housing opening. In this way, the tabs form a guide that forms a guide of the housing in the insertion direction of the electrically conductive plates and the at least one PTC resistance element, as a result of which the assembly is simplified. In addition to this, the tabs can be formed with a funnel-shape on the upper free end, in order to facilitate simple insertion of the two strip conductors with the at least one PTC resistance element arranged between them.